The present invention relates to a suspension or axle system for a vehicle, such as a bus or truck, wherein the rear wheels are steerable relative to the suspension system. The rear wheel steering system is intended to be utilized with a vehicle having combined therewith a conventional front wheel steering system.
It is well appreciated that a vehicle having steerable front and rear wheels provides the vehicle operator with many maneuvering advantages not available with a conventional front wheel only steering vehicle. While combined front and rear wheel steering systems have advantages for any type of vehicle, such combination is particularly useful with relatively long vehicles such as buses and trucks. Specifically, it is common that when such later vehicles turn a corner, they either have to make a very wide turn or, alternatively, in making a short turn the rear wheels of the vehicle are apt to either bump or ride over a curb. By having rear wheels that are steerable, the rear end of the vehicle may be kept away from a curb while the front end of the vehicle is making a relatively sharp turn.
As with companion application P-311 Rear Wheel Suspension System - Ewen, filed Dec. 23, 1988, it is not only an object of the present invention to provide a steerable rear wheel system, but also to combine such system with a suspension or dead axle device which enhances the roll or lateral stability for the vehicle. The stability is achieved basically in two ways. First, the unique axle design allows the body supporting springs to be located outboard in general longitudinal alignment with the steerable wheels. Second, the associated differential drive mechanism is mounted directly to the vehicle body and coacts with the axle to enable the body to be supported closer to the ground to thereby enhance stability as well as making easier the loading and unloading of the vehicle.
The basic suspension or axle system with which applicant's invention is combined is shown in U.S. Pat. No. 4,343,375 Vehicle Drive Wheel Suspension - Manning. The advantages of the Manning suspension as described in the aforementioned patent are also applicable to the present invention and are incorporated herein by reference. The primary advantages of the earlier Manning system is to provide a suspension wherein the unsprung weight of the system is greatly reduced by both supporting the differential from the vehicle body rather than the axle as well as in providing a dead axle system which is of a much lighter construction than conventionally forged axle systems.
The primary advantage of the subject suspension and steering system over the previously noted systems is in its simplification and reorganization of functional components that the present system is made to make it even lighter and less bulky than previous systems. The simplified construction of the present invention enables the ability of the vehicle body to be positioned closer to the ground further enhancing its lateral stability as well as making loading and unloading of the vehicle easier.